End fitting for tubular member

ABSTRACT

A fitting for connection to an end of a tubular member ( 204, 304 ), such as a hose or pipe, the fitting comprising a collar ( 202, 302 ) which is received over an outer surface of an end of the tubular member ( 204, 304 ), and a separate externally threaded sleeve ( 208, 308 ) which has an outside diameter which is larger than an internal diameter of the tubular member ( 204, 304 ), and is screwed into the tubular member ( 202, 304 ) to expand the tubular member and trap it between the collar ( 202, 302 ) and sleeve ( 208, 308 ).

This invention relates to end fittings for tubular members andparticularly, although not exclusively, relates to improved end fittingsfor high pressure hydraulic hoses.

BACKGROUND OF THE-INVENTION

Conventional hydraulic hose fittings are crimped or swaged to the end ofa hydraulic hose. FIG. 1 shows a conventional swaged hose fittingcomprising a collar 2 which fits over the outer surface of a hydraulichose 4.

A hydraulic connector 6 is connected to the hose 4 by means of anintegral sleeve 8 which is inserted into a bore 10 of the hose 4 untilthe connector 6 abuts an end of the hose 4. The position of the collar 2is adjusted such that it overlaps the hose 4 and connector 6. The collar2 is then forced radially inwardly in a direction D by means of acrimper or swager, until it assumes the orientation, illustrated in FIG.1, in which the hose 4 is compressed between the collar 2 and sleeve 8.

Although such fittings are generally reliable, they require an expensivecrimper or swager to assemble them. Furthermore, the bore 12 formed inthe sleeve 8 is either smaller than the bore 10 of the hose 4 at theoutset, or is reduced in diameter in the crimping or swaging process, sothat the fitting restricts the maximum flow which could otherwise passthrough the hose 4.

STATEMENTS OF INVENTION

According to the present invention there is provided a fitting forconnection to an end of a tubular member such as a hose or pipe, thefitting comprising a collar which is received over an outer surface ofan end of the tubular member, and a separate externally threaded sleevewhich has an outside diameter which is larger than an internal diameterof the tubular member, and which is screwed into the tubular member toexpand the tubular member and trap it between the collar and the sleeve.

Preferably, the collar is closely received over an outer surface of thetubular member.

Preferably, an internal bore of the collar is cylindrical. Preferably,the internal bore is smooth, as opposed to having surfacediscontinuities such as serrations, ridges or barbs.

Preferably, the sleeve forms a thread in an internal wall of the tubularmember as it is screwed in.

The thickness of a side wall of the sleeve may decrease towards itsdistal or leading end. For example, the distal end of the sleeve may bechamfered.

Preferably, the sleeve has an internal bore which is no smaller than aninternal bore of the tubular member prior to insertion of the sleeve.Preferably, the tubular member is a hose. Most preferably the tubularmember is a high pressure hydraulic hose.

Preferably, the sleeve is connected to a hydraulic connector at its endremote from a threaded end of the sleeve.

Preferably, the tubular member is formed from a polymer, such as Teflon.

Preferably, the tubular member comprises a resilient inner hose within abraided metal outer sheath.

Preferably, the thread on the threaded sleeve is 36 UNF or 28 UN onG-Line style pitch.

Preferably, the sleeve is provided with a secondary thread which engagesin a corresponding thread formed on the collar. Preferably, thesecondary thread is of larger diameter than the primary thread on thesleeve.

According to a second aspect of the present invention, there is provideda method of connecting a fitting to an end of a tubular member, themethod comprising the steps of:

(a) fitting a collar over a free end of the tubular member;

(b) screwing a threaded sleeve of the fitting, which sleeve has anoutside diameter larger than an internal diameter of the tubular member,into the tubular member, thereby expanding the tubular member andtrapping it between the collar and the sleeve.

According to a third aspect of the present invention there is provided afitting for connection to an end of a tubular member such as a hose orpipe, the fitting comprising a collar which is received over an outersurface of an end of the tubular member, and a separate sleeve which hasan outside diameter larger than an internal diameter of the tubularmember, and which is forced into the tubular member, thereby expandingthe tubular member and trapping it between the collar and the sleeve.

Preferably, the sleeve is threaded and is forced into the tubular memberby being screwed in. Preferably, the threaded sleeve forms acorresponding thread in an internal wall of the tubular member.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show moreclearly how it may be carried into effect, reference will now be made,by way of example, to the accompanying drawings, in which:

FIG. 1 shows a conventional swaged hose fitting;

FIGS. 2 a to 2 c show the principal steps in assembling a hose fittingin accordance with the present invention;

FIGS. 3 a to 3 c show the principal steps in assembling a hose fittingin accordance with an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 2 a shows a hose fitting for attachment to a hydraulic hose 204.The hose fitting comprises a cylindrical collar 202, and a hydraulicfitting 206 in the form of a banjo connector. The hydraulic fitting 206is machined in one piece with an integral cylindrical sleeve or tailpiece 208. The sleeve 208 is formed with an internal bore 207 whichextends from a distal end 205 of the sleeve 208 into a larger bore 209formed through the hose fitting 206. The sleeve 208 has an externalthread 211 which may for example be 36 UNF or 28 UN on G-Line stylepitch, and has a chamfered distal end 205.

In use of the hydraulic fitting, the collar 202 is pushed onto a freeend 201 of the hose 204 until the free end 201 of the hose 204 is flushwith a free end 203 of the collar 202. In order to aid in aligning thecollar 202 with the hose 204, an annular flange (not shown), whichprojects radially inwardly from the collar 202, may be provided at thefree end 203 of the collar 202. The hose 204 can then abut against theflange when the hose 204 is correctly positioned within the collar 202.

An internal bore d₁ of the hose 204, and the external diameter d₂ of thethread on the sleeve 208 are sized such that, as the sleeve 208 isscrewed into the hose 204, it forces the hose 204 radially outwardly andcuts a corresponding thread in the hose 204.

FIG. 2 b shows the sleeve 208 partially threaded into the hose 204, andFIG. 2 c shows the sleeve 208 fully seated. As illustrated in FIG. 2 c,as the sleeve 208 forces its way along the hose 204, the wall of thehose is forced radially outwardly against the collet 202, so that thereis a gradual reverse crimping or swaging action, in which the wall ofthe pipe 204 is trapped between the sleeve 208 and the collar 202.

It has been found experimentally that a hose connection made inaccordance with this embodiment of the invention is capable ofwithstanding a hydraulic pressure in excess of 8000 lb/in². However, inapplications where a very small hydraulic fitting is required, or whereconsistent high pressures are encountered, the hydraulic fitting can bemodified in the manner illustrated in FIGS. 3 a to 3 c. In thisembodiment, a secondary male MS thread 312 is formed on a proximal endof a shortened sleeve 308. This secondary thread 212 is of largerdiameter than the primary thread 311 formed on the sleeve 308. Acorresponding female thread 314 is formed in a distal end of a modifiedcollar 302. The principle of assembly of this embodiment is identical tothe previous embodiment. However, after the primary thread 311 on thesleeve 308 is engaged for substantially three quarters of its lengthwithin the bore 310 in the hose 304, the secondary male thread 312engages with the secondary female thread 314. This provides a directthreaded engagement between the collar 302 and the hydraulic fitting306. FIG. 3 b shows the point of engagement of the secondary male thread312 with the secondary female thread 314 and FIG. 3 c shows a fitting306 screwed fully into the hose 304 and collar 302.

Although the specific embodiment relates to a hydraulic fitting in theform of a banjo connector, the present invention is applicable toconnecting any type of fitting to a tubular member, such as a hose orpipe.

For example, it could be used in the assembly of a domestic plumbingfitting with appropriate selection of materials for the variouscomponents.

Preferably, the hose 204, 304 comprise a Teflon inner hose surrounded bya braided steel outer sheath. It is preferable that the material of thehose is able to be tapped by the primary thread 211, 311, but anymaterial is contemplated for the hose. Also the hose may be of one piececonstruction or may comprise any number or combination of inner or outerelements. Furthermore, the primary thread 211, 311 formed on the sleeve208, 308 may be of any suitable specification for the particularmaterials of the sleeve and hose. However, in experiments with Teflonhoses, a thread of 36 UNF or 28 UN on G-Line style pitch provedextremely effective and reliable.

1. A fitting for connection to an end of a tubular member, the fittingcomprising a collar which is received over an outer surface of an end ofthe tubular member, and a separate externally threaded sleeve which hasan outside diameter which is larger than an internal diameter of thetubular member, and which is screwed into the tubular member to expandthe tubular member and trap it between the collar and the sleeve. 2-18.(canceled)